Directionally biased staple and anvil assembly for forming the staple

ABSTRACT

In accordance with the present disclosure a directionally biased staple is provided for use in all types of surgical staplers having anvil structure against which the staple is formed. The directionally biased staple may be constructed in a wide variety of cross-sectional configurations including rectangular, elliptical, trapezoidal, etc. All of the configurations are distinguished by having a bending region requiring more force to twist or malform the staple than is required to properly form the staple. Preferably, these staples have Moment of Inertia Ratios on the order of between about 1.1 to about 3.0. The staple preferably corresponds in other respects to conventional formed staples, i.e. having at least a pair of leg members interconnected by a crown portion wherein the leg members are formed by direct contact with the anvil. An anvil assembly is also provided for minimizing the malformation of staples.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefits of andpriority to U.S. patent application Ser. No. 12/568,135, which was filedon Sep. 28, 2009, which is a continuation of U.S. Pat. No. 7,611,038,which was filed on Oct. 31, 2007, which is a continuation of U.S. Pat.No. 7,398,907, which was filed on Oct. 17, 2005, which is a continuationof U.S. patent application Ser. No. 09/972,594, which was filed on Oct.5, 2001 and which is currently abandoned, which is acontinuation-in-part of U.S. patent application Ser. No. 09/693,379which was filed on Oct. 20, 2000 and which is currently abandoned. Thereentire contents of all of which are incorporated herein in theirentirety by reference.

BACKGROUND

1. Technical Field

This invention relates to formable surgical fasteners and, moreparticularly, to directionally biased formable staples for use insurgical staplers having anvil pockets for forming the staples. Thisinvention also relates to anvil assemblies including anvil pockets foruse with surgical staplers.

2. Background of Related Art

Surgical stapling instruments have become critical to many life savingsurgical procedures. Surgical staples are usually mechanically insertedinto tissue with surgical stapling instruments such as those known asanastomosis devices, including gastrointestinal anastomosis devices andtransverse anastomosis devices. In such devices, the staples are loadedin one or more elongated rows into a cartridge. A mechanism for pushing,or driving the stapler is actuated to drive the staples through two ormore sections of tissue toward a deforming anvil. At the conclusion ofthe driving operation, the legs of each staple are conventionallyclamped or bent, by the anvil, to a closed configuration to complete thesuture and join the tissue sections together. Gastrointestinalanastomosis-type devices drive and bend the staples aligned in a rowsequentially in rapid sequence, while transverse anastomosis-typedevices drive and bend all staples simultaneously. See, e.g. U.S. Pat.Nos. 4,520,817 and 4,383,634. Circular anastomosis-type devicessimultaneously apply annular rows of staples to tissue. See, e.g. U.S.Pat. No. 4,304,236.

One type of conventional staple 20, shown in FIGS. 1-3, used with bothgastrointestinal anastomosis and transverse anastomosis-type surgicalstapling devices is made of stainless steel or titanium. The undeformedstaple 20 (FIG. 1) is generally U-shaped and includes a back span 22 andtwo legs 24 depending substantially perpendicularly from the back span.Each leg 24 has a sharp chiseled end point 26 for piercing body organsor tissue. The chisel point also creates torque in the staple, allowingit to form. The staple penetrates the tissue from one side to engage ananvil spaced apart and located at an opposing side of the tissue. Thestaple is bent by having the legs engage and follow an anvil 25 to forma B-shaped closed staple 28 as shown in FIG. 2. In this closedconfiguration tissue is compressed between the legs and backspan of thestaple.

Because of their substantially circular cross-section (FIG. 3), theseconventional staples require approximately the same amount of force toform the staple into its final shape as is required to twist or malformit.

For example, referring back to FIG. 3, a conventional round crosssection staple has a moment of inertia in the x forming dimension(I_(x)) given by the equation:

I _(x)=¼_(—) r ⁴

Its moment of inertia in the y twisting dimension (I_(y)) is given bythe same equation:

I _(y)=¼_(—) r ⁴

Using a round wire stock of uniform 0.009 in diameter (r=0.0045),

I_(x) = I_(y) = 1/4_(.0045)⁴ = 3.22 × 10⁻¹⁰  in⁴

The Moment of Inertia Ratio, given by the equation:

is I_(y)/I_(x)

$\frac{3.22 \times 10^{- 10}\mspace{14mu} {in}^{4}}{3.22 \times 10^{- 10}\mspace{14mu} {in}^{4}} = 1$

In order to insure accurate and consistent formation of theseconventional staples, considerable research and development has beenconducted in the areas of forming and driving structures. For example,anvils have been developed with specific coatings and/or structure, see,e.g. U.S. Pat. Nos. 5,173,133 and 5,480,089. Also, staple cartridgeshave been configured with driver structure to balance forces encounteredduring staple formation. See, commonly assigned U.S. Pat. No. 4,978,049to Green. Thus, to control and insure consistent staple formationwithout twisting or deformation, extremely strict manufacturingtolerances have been implemented.

Other types of staples for different types of instruments are also foundin the prior art. Some have non-circular cross-section. FIGS. 4, 4A and4B illustrate by way of example a staple of this type marketed by UnitedStates Surgical of Norwalk, Conn. for use with its MULTIFIRE ENDO HERNIAand ENDO UNIVERSAL 65 staplers. The anvil in these staplers, as shown inFIGS. 4C and 4D, is adjacent the backspan of the staple as tissue isapproached from only one side. Unlike the staples described above whichare formed by contact of the staple legs with anvil pockets, thesestaple legs are bent around an anvil abutting the backspan. This staplehas a side portion H with a height dimension greater than the dimensionof the base portion B (i.e. 0.020 in vs. 0.015 in.).

The Moment of Inertia Ratio is given by the equation:

$\begin{matrix}{{{Moment}\mspace{14mu} {of}\mspace{14mu} {Inertia}\mspace{14mu} {Ratio}} = \frac{I_{y}}{I_{x}}} \\{= \frac{{Moment}\mspace{14mu} {of}\mspace{14mu} {Inertia}\mspace{14mu} {About}\mspace{14mu} {Twisting}\mspace{14mu} {Axis}}{{Moment}\mspace{14mu} {of}\mspace{14mu} {Inertia}\mspace{14mu} {About}\mspace{14mu} {Forming}\mspace{14mu} {Axis}}}\end{matrix}$

where I_(x)=( 1/12)bh³ and I_(y)=( 1/12)hb³, with h=0.020 in. andb=0.015 in.

Thus, I_(x)=( 1/12)(0.015)(0.020)³=1.0×10⁻⁸ in⁴, and I_(y)=(1/12)(0.020)(0.015)³=6.0×10⁻⁹ in⁴. Accordingly,

${{Moment}\mspace{14mu} {of}\mspace{14mu} {Inertia}\mspace{14mu} {Ratio}} = {\frac{6.01 \times 10^{- 9}\mspace{14mu} {in}^{4}}{1.10 \times 10^{- 8}\mspace{14mu} {in}^{4}} = {{{.60}/1} = {.60}}}$

This staple is specifically configured to accommodate twisting duringstaple formation to permit the legs of the staple to cross as shown inFIG. 4E. Thus, it is engineered so the force to form the staple isslightly greater than the force to malform or twist the staple. Theforming is accomplished by bending the staple legs around an anvilpositioned adjacent the inner surface 32 of the backspan 34.

U.S. Pat. No. 5,366,479 describes a hernia staple with adjacent anvilhaving a height of 0.38 mm and a thickness of 0.51 mm. This staple isformed the same way as in FIGS. 4C and 4D. The moment of inertia ratioof this staple in accordance with the foregoing formula is as follows:

I_(x) = (1/12)(.51)(.38)³ = 2.33 × 10⁻³I_(y) = (1/12)(.38)(.51)³ = 4.2 × 10⁻³${{Moment}\mspace{14mu} {of}\mspace{14mu} {Inertia}\mspace{14mu} {Ratio}} = {\frac{4.2 \times 10^{- 3}}{2.33 \times 10^{- 3}} = 1.8}$

This staple for use as described would actually result in greater forceto produce the desired shape. In fact, the staple legs would likelycontact each other before crossing over into their crossedconfiguration.

Thus, it is apparent that this type of hernia staple, i.e. where theanvil is adjacent the backspan as the tissue is approached from only oneside, is quite different than the staple of the present invention, e.g.the B-shaped staple, wherein the legs penetrate through the tissue tocontact anvil pockets. These anvil pockets direct the staple legs toform the staple into a closed configuration. Thus staple configurationand considerations of twisting, bending and staple formation of thesehernia staples are inapplicable to these considerations for anvil pocketdirected staples, such as the B-shaped staples.

It would therefore be desirable to provide a staple configuration for astaple designed to penetrate tissue and contact an anvil pocket on theopposing side of tissue, which, in complement with conventionalcartridge and anvil technology, enhances correct staple formation whilereducing twisting/malformation caused by misalignment or unusual tissuewhile minimizing reliance on strict manufacturing tolerances. It wouldalso be desirable to provide an anvil assembly which would minimizestaple malformations by misalignment or twisting during formation of thestaple.

SUMMARY

In accordance with the present disclosure a directionally biased stapleis provided for use in surgical staplers having anvil structure spacedfrom the cartridge and having anvil pockets against which the staple isformed as the legs are forced into contact with the anvil. Thedirectionally biased staple may be constructed in a wide variety ofcross-sectional configurations including rectangular, elliptical,trapezoidal, etc. All of the configurations are distinguished by havinga bending region requiring more force to twist or malform the staplethan is required to properly form the staple. Preferably, these stapleshave Moment of Inertia Ratios on the order of between about 1.1 to about3.0. The staple preferably corresponds in other respects toconventionally formed staples, i.e. having at least a pair of legmembers interconnected by a crown portion wherein the leg members comeinto contact with and are formed by the anvil.

An anvil assembly is also provided which includes a tissue engagingsurface and a plurality of staple pockets formed therein and configuredto improve the formation of a staple during formation of the staple.Each staple pocket includes a pair of staple forming cups and achanneling surface positioned at least partially about each cup. Eachcup includes an inside portion and an outside portion. The insideportion of each cup is positioned adjacent the inside portion of theother cup. Each cup includes a sidewall which defines an angle withrespect to the tissue engaging surface which approaches perpendicular ina direction moving from the outside of the cup portion towards theinside portion of the cup. The sidewall defining at least the insideportion of each cup is substantially perpendicular to the tissueengaging surface of the anvil assembly such that each staple formingpocket defines a substantially vertical trap for minimizing misalignmentand malformation of a staple.

BRIEF DESCRIPTION OF THE DRAWINGS

Various preferred embodiments are described herein with reference to thedrawings, wherein:

FIG. 1 is a side view of a conventional staple as known in the art;

FIG. 2A is a side view of the staple of FIG. 1 formed into a “B”configuration;

FIGS. 2B, 2C and 2D illustrate the staple of FIG. 2 being formed as thelegs, after penetrating tissue, come into contact with the anvilpockets;

FIG. 3 is a cross-sectional view of the staple of FIG. 1 taken alongline 3-3;

FIG. 4 is a perspective view of a conventional rectangular cross-sectionstaple as known in the art which is formed around an anvil contacted bythe backspan;

FIG. 4A is a side view of the staple of FIG. 4.

FIG. 4B is a cross-sectional view of the staple of FIG. 4 taken alongline 4B-4B;

FIGS. 4C, 4D and 4E illustrate the staple of FIG. 4 being formed as thelegs are bent by the pusher and the backspan is held against the anvil;

FIG. 5 is a side view of a directionally biased staple in accordancewith the present disclosure;

FIG. 6 is a perspective view of the staple of FIG. 5;

FIG. 7 is a top view of the staple of FIG. 5;

FIG. 8 is a cross-sectional view of the staple of FIG. 5 taken alongline 8-8;

FIG. 9A is a side view of the staple of FIG. 5 after it has beendeformed to a “B” configuration;

FIG. 9B is an end view showing the coplanarity of the AB@ sections ofthe staple of FIG. 9A;

FIGS. 10A B 10F are side views showing staple formation of the staple ofFIG. 5 as the staple penetrates tissue and the legs come into contactwith the anvil pockets;

FIG. 11A graphically illustrates the comparison of the mean twist (ininches) vs the offset of the conventional staple of FIG. 1 and the novelstaple of FIG. 5.

FIG. 11B graphically illustrates the comparison of the mean twist (in %)vs the offset of the conventional staple of FIG. 1 and the novel stapleof FIG. 5;

FIG. 12A is a cross-sectional view of another embodiment of adirectionally biased staple in accordance with the present disclosure;

FIG. 12B is a cross-sectional view of another embodiment of adirectionally biased staple in accordance with the present disclosure;

FIG. 12C is a cross-sectional view of another embodiment of adirectionally biased staple in accordance with the present disclosure;

FIG. 13 is a cross-sectional view of another embodiment of adirectionally biased staple in accordance with the present disclosure;

FIG. 14 is a cross-sectional view of another embodiment of adirectionally biased staple in accordance with the present disclosure;

FIG. 15 is a perspective view of an endoscopic gastrointestinalanastomosis-type device for firing the staple of FIG. 5;

FIGS. 16-16C are enlarged views showing the staple formation by theanvil pockets of the instrument of FIG. 15;

FIG. 17 is a perspective view of a gastrointestinal anastomosis-typedevice for firing the staple of FIG. 5;

FIG. 18 is a perspective view of a transverse anastomosis-type devicefor firing the staple of FIG. 5;

FIG. 18A is an enlarged view of the staple forming anvil and a portionof the disposable loading unit of the device of FIG. 18;

FIGS. 18B and 18C are enlarged views showing the staple formation by theanvil pockets of the instrument of FIG. 18A;

FIG. 19 is a perspective view of a circular anastomosis-type device forfiring the staple of FIG. 5;

FIG. 19A is an enlarged view of the staple forming anvil and a portionof the disposable loading unit of the device of FIG. 19;

FIGS. 19B and 19C are enlarged views showing the staple formation by theanvil pockets of the instrument of FIG. 19A;

FIG. 20 is a perspective view of another embodiment of a directionallybiased staple in accordance with the present disclosure;

FIG. 21 is a cross-sectional view taken along section lines 21-21 ofFIG. 20;

FIG. 22 is a front elevational view of the directionally biased stapleshown in FIG. 20 after the staple has been deformed to the B-shapedconfiguration;

FIG. 23 is a side elevational view from the direction of lines 23-23 ofFIG. 22;

FIG. 24 is a perspective view of an anvil adapted for attachment to anendoscopic gastrointestinal anastomosis-type device;

FIG. 25 is an enlarged view of the indicated area of detail shown inFIG. 24;

FIG. 26 is a top partial cutaway view of the anvil shown in FIG. 24;

FIG. 27 is a cross-sectional view taken along section lines 27-27 ofFIG. 26;

FIG. 28 is a cross-sectional view taken along section lines 28-28 ofFIG. 26;

FIG. 29 is another enlarged top view of a portion of the anvil assemblyshown in

FIG. 25;

FIG. 29 a is a cross-sectional view taken along section lines 29 a-29 aof FIG. 29;

FIG. 29 b is a cross-sectional view taken along section lines 29 b-29 bof FIG. 29;

FIG. 29 c is a cross-sectional view taken along section lines 29 c-29 cof FIG. 29;

FIG. 29 d is a cross-sectional view taken along section lines 29 d-29 dof FIG. 29;

FIG. 29 e is a cross-sectional view taken along section lines 29 e-29 eof FIG. 29;

FIG. 29 f is a cross-sectional view taken along section lines 29 f-29 fof FIG. 29;

FIG. 29 g is an alternative embodiment of the cross-sectional view takenalong section lines 29 c-29 c of FIG. 29; and

FIG. 30 is a graph illustrating force vs. deformation of a staple beingformed in a pocket of the anvil shown in FIG. 24.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the presently disclosed directionally biasedstaple will now be described in detail with reference to the drawings,in which like reference numerals designate identical or correspondingelements in each of the several views.

A directionally biased staple 50 in accordance with one embodiment ofthe present disclosure is illustrated in FIGS. 5-9. Referringspecifically to FIGS. 5-7, staple 50 has a U-shaped configuration andincludes a pair of substantially parallel legs 52 connected by a crownportion 54 with a bending region 55 therebetween. The legs are shownperpendicular to the backspan and are substantially straight along theirlength. Tissue penetrating portions 56 are preferably formed adjacent adistal end of legs 52. These penetrating portions 56 may be of any knownconfiguration which facilitates entry of the legs 52 into tissue to bestapled. As shown in FIG. 5, the tissue penetrating portions 56 arepreferably formed in a chisel shape with points 58 adjacent inner facingsides of legs 52.

In this embodiment, the cross section is preferably formed in asubstantially rectangular configuration as shown in FIG. 8 with xdesignating the major base dimension (b) and y designating the minorheight dimension (h) of the crown portion of the staple when positionedin an inverted-U configuration as shown in FIG. 5. As used herein, thestaple is intended to be formed about the x dimension (x axis). Thus, asillustrated in FIGS. 10A-10F staple 50 is formed downward relative tothe page.

This cross-sectional configuration may be achieved by any known methodincluding extrusion, rolling, coining, etc. Preferably, thisconfiguration is accomplished by flat rolling round wire stock onopposing sides. In the fabrication process, the stock can be pre-rolledby the wire manufacturer or may be round wire stock which is rolled intothe desired cross-sectional configuration by the staple manufacturer.

I_(Y) of the cross-sectional configuration of the novel stapleillustrated in FIG. 5 is given by the equation:

I _(y)=( 1/12)(b)³(h)

For a base dimension b=0.010 in and a height dimension h=0.008 in,

I _(y)=( 1/12)(0.010)³(0.008)

I _(y)=6.67×10⁻¹⁰ in⁴

I_(x) is given by the equation:

I _(x)=( 1/12)(b)(h)³

I _(x)=( 1/12)(0.010)(0.008)³

I _(x)=4.26×10⁻¹⁰ in⁴

The Moment of Inertia ratio (I_(y)/I_(x)) is thus

$\frac{6.67 \times 10^{- 10}\mspace{14mu} {in}^{4}}{4.26 \times 10^{- 10}\mspace{14mu} {in}^{4}} = 1.57$

Similarly, for a base dimension b=0.012 in and a height dimensionh=0.008 in, I_(x)=1.0×10⁻⁹ in⁴ and I_(y)=5.12×10⁻¹⁰ in⁴, yielding aMoment of Inertia ratio of 1.95.

Given that I_(y) defines the dimension corresponding to proper formationof the staple when fired and I_(x) defines the dimension correspondingto twisting and/or malformation, it is readily apparent that thedirectionally biased configurations provide a “functionally similar”forming force as a conventional round staple while requiring up to twiceas much force to twist or malform when compared to conventional staples.This novel staple provides a substantial improvement over conventionalstaples.

Table 1 below sets forth by way of example Moment of Inertia Ratios fora variety of sizes and types of novel directionally biased staples foruse in surgical staplers. Clearly staples of other dimensions arecontemplated so long as they have the novel moment of inertia ratiodescribed herein.

I_(y)/I_(x) Moment Staple Height Base of Inertia Size (in.) (in.) I_(y)I_(x) Ratio 3.5 mm. .007 .010 5.83 × 10−10 2.86 × 10−10 _2.04/1 Titanim3.5 mm. .007 .0115 8.87 × 10−10 3.29 × 10−10 _2.70/1 Stainless Steel 3.8mm. .007 .010 5.83 × 10−10 2.86 × 10−10 _2.04/1 Stainless Steel 4.8 mm..009 .014 2.00 × 10−9  8.51 × 10−10 _2.35/1 Titanim 4.8 mm. .007 .01158.87 × 10−10 3.29 × 10−10 _2.70/1 Titanim

Further, as illustrated below, for comparable size staples, the novelstaple configuration provides increased resistance to twist withoutchanging firing forces.

For example, twisting stress _b is defined by the equation:

$\;_{\_ b} = \frac{M\; c}{I_{y}}$

with moment M kept constant at M=1 lb$in.

For a conventional round 0.009 in. diameter staple: M=11 b$in; c=0.0045in; and I_(x)=I_(y)=3.22×10⁻¹⁰ in⁴, so

$\;_{\_ b} = \frac{\left( {1.0\mspace{14mu} {lb}\mspace{14mu} {in}} \right)\left( {{.0045}\mspace{14mu} {in}} \right)}{3.22 \times 10^{- 10}\mspace{14mu} {in}^{4}}$ _(_b) = 13, 975  ksi

For the directionally biased staple of FIG. 8 having b=0.010 in andh=0.008 in: M=1.0 lb$in; c=0.005 in; and I_(y)=6.67×10⁻¹⁰ in⁴.

$\;_{\_ b} = \frac{\left( {1.0\mspace{14mu} {lb}\mspace{14mu} {in}} \right)\left( {{.005}\mspace{14mu} {in}} \right)}{6.67 \times 10^{- 10}\mspace{14mu} {in}^{4}}$ _(_b) = 7, 496  ksi

Thus, not only is this embodiment of the novel staple more resistant totwisting and/or malformation, e.g. _(—)14,000 ksi for the conventionalstaple vs. _(—)7,500 ksi for the novel staple, it also maintains minimalfiring forces. The directionally biased staple is effectivelydesensitized against the effects of misalignment during staple formationwhile, at the same time maintaining a minimal firing force. Thisdirectionally intelligent design can reduce malformations caused bymisalignment or twisting as well as reduce the need for very sensitivemanufacturing tolerances for anvils and anvil forming cups, cartridges,etc.

The benefits of the novel staple can also be appreciated by reference tothe graphs of FIGS. 11A and 11B. Since staples are forced through thicktissue and the staple cartridge and anvil can flex as tissue iscompressed and can move slightly relative to another, this affects thepoint of contact between the staple leg points and the anvil. Forexample, if the anvil moves slightly out of alignment, the staple legswill contact a different point of the anvil which can affect uniformformation of the staple. Additionally, due to manufacturing tolerances,the staple points may not contact the anvil in the exact optimallocation. Although such staple formation is clinically satisfactory andeffective, the novel staple of the present application provides for moreuniform formation of the row of staples and accommodates formanufacturing tolerances as it is more resistant to twisting. That is,the staple will have the tendency to bend in the direction of thethinner dimension which is desired since in this case the thinnerdimension defines the desired bending direction. By relaxingmanufacturing tolerances, the cost of manufacturing is reduced as well.

As shown in FIG. 11A, the prior art round staple, since the height andwidth are the same, can twist in different directions if there ismisalignment between the staple and anvil. Thus the direction oftwisting cannot be controlled. In contrast, the Moment of Inertia ratioof the novel staple of the present invention results in reducedtwisting. Note that not only is there more twisting initially with theprior art staple, but as the offset increases, the amount of twisting inthe current staple is greater at any degree of offset. The percentage oftwist is defined as x/d x 100% wherein x is the distance between thecenterline of the staple and d is the diameter (or width) of the staple.

FIGS. 12-14 illustrate alternate directionally biased cross-sectionalconfigurations in accordance with the disclosure. These cross-sectionalconfigurations all have aspect ratios in the range of about 1.1 to about3.0 wherein the x axis designates the major base dimension (b) and they-axis designates the minor height dimension (h) in each of thesecross-sections.

FIGS. 15-19 disclose by way of example several types of surgicalstaplers which can utilize the novel directionally biased staples. Othertypes of surgical staplers are also contemplated.

FIG. 15 illustrates a known endoscopic sequential stapler 100 includingan anvil 110 and a staple cartridge 102 having novel directionallybiased staples 50 loaded into the staple cartridge 102 thereof.Referring to FIGS. 16-16C, with anvil 110 and staple cartridge 102 in anopen position (FIG. 16), tissue 120 is positioned between anvil 110 andcartridge 102 (FIG. 16A). Anvil 110 is now pivoted in the directionindicated by arrow “A” towards cartridge 102 (FIG. 16B) in a knownmanner to compress tissue 120 between anvil 110 and staple cartridge102. Thereafter, staples 50 are ejected from staple cartridge 102 intopockets 122 formed on anvil 110. Pockets 122 deform staples 50 into asubstantially B-shaped configuration (FIG. 16C). Anvil 110 can now bepivoted to the open position to permit tissue 120 to be removed fromstapler 100.

FIG. 17 illustrates a known open type sequential stapler 150 includingan anvil 152 and a staple cartridge 154 having novel directionallybiased staples loaded therein. Ejection of staples from stapler occursin a manner similar to that disclosed in FIGS. 16-16C and will not bediscussed in further detail herein.

FIG. 18 illustrates a known transverse type surgical stapler 200including an anvil 210 and a staple cartridge 202 having noveldirectionally biased staples 50 loaded into the staple cartridge 202.Referring to FIGS. 18A-18C, with anvil 210 and staple cartridge 202 inan open position, tissue 220 is positioned therebetween (FIG. 18A).Anvil 210 is now moved in the direction indicated by arrow “B” to anapproximated position towards cartridge 202 (FIG. 18B) in a known mannerto compress tissue 220 between anvil 210 and staple cartridge 202.Thereafter, staples 50 are ejected from staple cartridge 202 intopockets 222 formed on anvil 210. Pockets 222 deform staples 50 into asubstantially B-shaped configuration (FIG. 18C). Anvil 210 can now bemoved to the open position to permit tissue 220 to be removed fromstapler 200.

FIG. 19 illustrates a circular stapler 300 including an anvil 310 and astaple cartridge 302 having the novel directionally biased staples 50loaded in the staple cartridge 302. Referring to FIGS. 19A-19C, withanvil 310 and staple cartridge 302 in an open position, tissue 320 ispositioned therebetween (FIG. 19A). Anvil 310 is now moved towardscartridge 302 in a known manner to compress tissue 320 between anvil 310and staple cartridge 302 (FIG. 19B). Thereafter, staples 50 are ejectedfrom staple cartridge 302 into pockets 322 formed on anvil 310. Pockets322 deform staples 50 into a substantially B-shaped configuration (FIG.19C). Anvil 110 can now be moved to the open position to permit tissue320 to be removed from stapler 300.

FIGS. 20-23 illustrate another preferred embodiment of the presentlydisclosed directionally biased staple shown generally as 400.Directionally biased staple 400 includes a crown portion 410 and a pairof outwardly angled legs 412 with a bending region 414. Legs 412 definean angle about 5° to about 15° with crown portion 410. Preferably, legs412 define an angle of about 9< with respect to crown portion 410.Alternately, other angle orientations are envisioned. The angle of legs412 function to retain the staple within staple receiving slots of astaple cartridge prior to use, i.e., legs 412 frictionally engage theslot walls of a staple cartridge to retain the staple within a cartridgeslot. Tissue penetrating portions 416 are formed at the distal end oflegs 412 and preferably have a chisel shape with points 418 adjacentinner facing sides of legs 412. Referring to FIG. 21, staple 400 has across-section having flat top and bottom surfaces 420 and 422 andsemi-circular side surfaces 424 and 426. Preferably, this cross-sectionis achieved by rolling top and bottom surfaces of wire stock.Alternately, other methods including extrusion and coining may be usedto form staple 400. Using the appropriate formulas, the Moment ofInertia ratio of staple 400 is approximately 2. Alternately, thedimensions of staple 400 may be varied in a manner to achieve a Momentof Inertia ratio within the preferred range of about 1.1 to about 3.FIGS. 22 and 23 illustrate staple 400 in the formed state wherein staple400 assumes a B-shaped configuration.

There are various methods of manufacturing the surgical staple. Forexample, the method could include the steps of flat rolling the wirestock to form at least one flat surface thereon and cutting a length ofround wire stock to a predetermined length corresponding to a desiredlength of a finished staple or extruding the stock with a flat surface.The stock is bent into a form having a backspan and a pair of legswherein the staple has an aspect ratio of between about 1.1 to about3.0.

FIGS. 24-28 illustrate an anvil 500 which is configured for attachmentto a transverse-type surgical stapler such as shown in FIG. 18. Anvil500 includes a plurality of staple pockets 510 formed in the surface ofthe anvil. Each staple pocket 510 includes first and second stapleforming cups 512 and 514 and a channeling surface 516 disposed aroundeach of the staple forming cups. An anvil including such a stapleforming pocket has been disclosed in U.S. Pat. No. 5,480,089 filed Aug.19, 1994, the entirety of which is incorporated herein by reference.Anvil 500, including staple forming cups 512 and 514 and channelingsurface 516 can be adapted for use with any of the surgical staplingdevices described in the specification above including endoscopicgastrointestinal anastomosis-type devices (FIG. 15), gastrointestinalanastomosis-type devices (FIG. 17), transverse anastomosis-type devices(FIG. 18) and circular anastomosis-type devices (FIG. 19). U.S. patentapplication Ser. No. 09/687,815, filed Oct. 13, 2000, discloses atransverse anastomosis-type device including such an anvil assembly.This application is incorporated herein in its entirety by reference.

FIGS. 29-29 f illustrate in greater detail anvil assembly 500 shown inFIGS. 24-28. Anvil assembly 500 includes an anvil plate 508 defining atissue contact surface 502 and having a plurality of staple pockets 510formed in surface 502 of the anvil plate 508. As discussed above, eachstaple pocket 510 includes first and second staple forming cups 512 and514 and a channeling surface 516 formed about at least a portion(preferably the majority) of each of the staple forming cups 512 and514. Each staple forming cup 512 and 514 is defined by sidewalls 520 andan elongated base surface 518. As shown in FIG. 29 a each staple formingcup 512, 514 includes an outside portion O, a central portion C, and aninside portion I. Outside portion O extends from the outer extent of theforming cup (shown in FIG. 30 f) to central portion C of the forming cupat and about the deepest portion of the forming cup (see the ends oflead lines of reference numbers 512 and 514 in FIG. 28). Inside portionI of each forming cup extends from central portion C of the forming cupto the highest operative staple leg or tip engaging point at or nearapex 515 of each pocket 510 (See FIG. 29 a). Base surface 518 extendsaxially from adjacent the outer extent of the outside portions of eachof the staple forming cups 512 and 514, as shown in FIG. 29 f, throughthe central and inside portions of each of the staple forming cups 512and 514 and terminates at or near the apex 515 of pocket 510 (e.g., seeFIG. 29 a).

Elongated base surface 518 is substantially linear, i.e., substantiallyflat (herein understood to include flat), along its transverse axis andis concavely or curved along its longitudinal axis. The substantiallylinear surface preferably corresponds to the shape of the points of astaple to be formed thereagainst. Since the preferred staple hassubstantially linear tips (See staple 400 in FIGS. 20-22), the preferredbase surface for such a staple is substantially linear. This providesline-to-line contact between the flat surfaces of the staple tips andthe substantially linear base surface. By providing a base surfacehaving a shape that corresponds to the shape of the staple point,friction is reduced and galling of the staple tip during stapleformation is minimized. The shape of base surface 518 may be altered toconform to the shape of the staple points of different staples, whichmay be rounded, triangular, etc.

In the preferred embodiment shown, sidewalls 520, which partly definestaple forming cups 512 and 514, are angular as they extend from thelower portion of the channeling surface to base surface 518. Side walls520 gradually become progressively more vertical (or perpendicular inrelation to tissue contact surface 502) along elongated base surface 518starting from the outer extent of outside portion O of cups 512 and 514where sidewalls 520 are widely angular [relative to tissue contactsurface 502 or to the vertical axis VA of the pocket (FIG. 30 f)]towards and through central portion C and inside portion I of cups 512and 514. Preferably, the central and inside portions of cups 512 and 514are defined by substantially vertical (herein understood to includevertical) sidewalls 520, such that a substantially vertical trap 522 isformed at least in the central and inside portions of each stapleforming cup. The substantially vertical trap can start at any suitablelocation along the longitudinal axis of staple forming cup 512, 514(FIG. 30). While it is preferred that the trap begin in outside portionO of the staple forming cup before or when the first peak force occurs(FIG. 30), properly formed staples in accordance with the invention canalso be obtained when the substantially vertical trap starts in thecentral or inside portion of the staple forming cup. Briefly,substantially vertical trap 522 functions to align and accurately formstaples therein. The substantially vertical trap can be of any suitablelength depending on, for example, the dimensions and configuration ofthe particular staple and staple forming cup, and the desiredconfiguration of the finished staple. The length of substantiallyvertical trap 522 is preferably between about 0.5r and about 2r, where ris the radius of curvature of each pocket, and more preferably, thelength of the vertical trap is about r. A preferred radius r is fromabout 0.030 inch to about 0.100 inch, more preferably about 0.050 inch,herein understood to include 0.054 inch.

Referring to FIG. 30, as a staple is formed against an anvil, the forceapplied to the staple typically will increase as the staple moves intothe staple pocket until the force is sufficient to buckle or plasticallydeform the staple. This peak force applied to the staple isschematically illustrated in the graph shown in FIG. 30 by the letterAX® and typically occurs first when the tips of the legs of a stapleengage base surface 518 in the outside portion of cups 512 and 514,where the legs begin to plastically deform. The first peak forcetypically occurs when the tips of the staple legs strike base surface518 and move approximately between the positions shown in FIGS. 10B and10C. A second peak force identified by the letter AY@ in the graph shownin FIG. 30 is applied to the staple to bend the staple legs upwardly.The second peak force Y typically occurs when a portion of the legs ofthe staple is positioned in engagement with base surface 518, also inoutside portion O, of cups 512 and 514 approximately between thepositions shown in FIGS. 10D and 10E. Staple pockets 510 of anvilassembly 500 are preferably configured as a trough that preferablygradually funnels and directs movement of the staple tips and legs of astaple being formed into the substantially vertical trap at least by thetime peak forces X and Y are reached. The substantially vertical trapcaptures the tips and the legs of the staples within and along the trap,preferably including during the peak loads of staple formation.Capturing the tip and legs of a staple herein means that at least aportion, preferably the base portion, of the sidewalls of thesubstantially vertical trap of the staple forming cup closely confinesthe staple tips and legs in a slip fit relationship to minimize lateralor transverse movement of the tips and legs and positively direct thestaple through the substantially vertical trap portion of the stapleforming cup. By doing so, malformation by misalignment or twisting ofthe staple is minimized or eliminated.

FIGS. 29 b-29 f show that side walls 520 with base surface 518 form atrough that gradually funnels the tips and legs of a staple from outsideportion O of cups 512 and 514 into a substantially vertical trap in theoutside, central and inside portions O, C and I, respectively, of thecups, and terminates at or near apex 515 of cups 512 and 514.

FIG. 29 f shows that the outside portion O of staple forming cup 514 iswidely angled relative to tissue forming surface 502 or vertical axis VAto provide a large target area to receive the tips of the staple legs asthey are fired into anvil pocket 510.

FIG. 29 e, also taken through outside portion O of forming cup 514,shows that sidewalls 520 are at a sharper angle relative to verticalaxis VA to more closely guide the staple tips and legs along forming cup514.

FIG. 29 d shows that the sidewalls 520 along inside portion I, althoughat an angle of about 8°, are substantially vertical relative to verticalaxis VA. In FIGS. 29 c and 29 b, the sidewalls are shown as vertical.Ideally and most preferably a major portion of sidewalls 520 of thesubstantially vertical traps are actually vertical. It is to beunderstood that in attempting to obtain a vertical sidewall, whether thesidewalls are actually vertical or are substantially vertical may dependon how the anvil pockets are formed. Preferably, for economic reasonsand ease of manufacture, the anvil is formed from a thin sheet of metaland the pockets are stamped therein. Since there is some spring back,i.e., elastic deformation, during cup formation by stamping, thesidewalls of the cups will in some instances actually be substantiallyvertical. If the anvil is cast or machined, the sidewall typically trulywill be vertical. Thus, in accordance with the invention, the object isto provide a trough that funnels and guides the staple tips and legsinto an elongated substantially vertical trap that traps or captures andpositively directs the staple tips and the legs within and along thesubstantially vertical trap in its path to or near the apex as thestaple is formed. While it is preferred that the sidewalls of the stapleforming cups that lead to the substantially vertical trap be angular,such is not essential. Such sidewalls and/or upper portions of thesidewalls along the substantially vertical trap can be arcuate (520′,FIG. 29 g) or otherwise shaped, so long as enough of the height of theor a lower portion, e.g., “L”, of the sidewalls of the substantiallyvertical trap are substantially vertical in order to trap the staple inaccordance with the invention. It is contemplated that “enough of theheight of the or a lower portion of the sidewall” means that the heightis at least about ½ of the thickness or diameter of the particularstaple being formed. It is contemplated that substantially verticalsidewalls are those that are less than about 20° relative to thevertical axis, preferably less than about 15° and more preferably lessthan about 10°.

While the parameters of the start, length, configuration and end of thevertical trap and the substantially vertical disposition of thesidewalls has been attempted to be explained, it is understood thatthese parameters can vary depending on various factors, for example, thestarting staple configuration and its dimensions and desired finalshape, so long as the principle of capturing the tips and legs of astaple in a substantially vertical trap is present or employed tocapture and positively and direct the movement and direction of thestaple to optimize proper staple formation.

The employment of substantially vertical traps in staple forming cups,especially those having a substantially linear base surface isespecially advantageous for use in connection with the directionallybiased staples disclosed herein, particularly those having substantiallylinear tips. This combination is particularly effective in compensatingfor variations in the staple manufacturing and forming systems tominimize the occurrence of malformed staples, including those malformedbecause of variations in the density of the tissue to be stapled, instaple shape, geometry, or material, and in the configuration of thestaple tips, e.g., uneven angular or rounded.

Although specific embodiments of the present disclosure have beendescribed above in detail, it will be understood that this descriptionis merely for purposes of illustration. Various modifications of andequivalent structures corresponding to the disclosed aspects of thepreferred embodiment in addition to those described above may be made bythose skilled in the art without departing from the spirit of thepresent disclosure which is defined in the following claims, the scopeof which is to be accorded the broadest interpretation so as toencompass such modifications and equivalent structures.

1. An anvil assembly for use with a surgical stapler, the anvil assemblycomprising: a tissue contact surface; a plurality of staple pocketsformed in the tissue contact surface, each of the plurality of staplepockets defining a longitudinal axis; and each of the plurality ofstaple pockets including first and second staple forming cups, each ofthe first and second staple forming cups having an outside portion andan inside portion, the inside portion of the first and second stapleforming cups being positioned in close relation to each other on thelongitudinal axis of each of the plurality of staple pockets, theoutside portion of the first and second staple forming cups beingpositioned in spaced relation to each other on the longitudinal axis ofeach of the plurality of staple pockets, each of the first and secondstaple forming cups being defined by sidewalls and an elongated basesurface extending along the longitudinal axis of each of the pluralityof staple pockets; wherein the elongated base surface includes atransverse width, and wherein a distance between a longitudinal edge ofthe elongated base of the first staple forming cup and a longitudinaledge of the first staple forming cup is approximately equal to thetransverse width of the elongated base surface.
 2. A surgical stapler,comprising: an anvil assembly, comprising: a tissue contact surface; aplurality of staple pockets formed in the tissue contact surface, eachof the plurality of staple pockets defining a longitudinal axis; each ofthe plurality of staple pockets including first and second stapleforming cups, each of the first and second staple forming cups having anoutside portion and an inside portion, the inside portion of the firstand second staple forming cups being positioned in close relation toeach other on the longitudinal axis of each of the plurality of staplepockets, the outside portion of the first and second staple forming cupsbeing positioned in spaced relation to each other on the longitudinalaxis of each of the plurality of staple pockets, each of the first andsecond staple forming cups being defined by sidewalls and an elongatedbase surface extending along the longitudinal axis of each of theplurality of staple pockets, wherein a distance between a longitudinaledge of the elongated base of the first staple forming cup and alongitudinal edge of the first staple forming cup is approximately equalto a transverse width of the elongated base surface; and a staplecartridge, comprising: a plurality of directionally biased staplessupported in a spaced relation to each other, each of the directionallybiased staples including, a crown portion; and a pair of legs dependingfrom the crown portion, the pair of legs being positioned to be receivedwithin a respective staple pocket of the anvil assembly for formation ofthe staple.